This is a good book, thorough and well-researched. Besides a few typos (which is not really the author's fault), the book is enjoyable and for its small size (not even 150 pages!), very thorough. The only criticisms I have are:
1. the author's use of the Gospel of Barnabas in the section which discusses the substitute theory, even though this Gospel is not considered to be authentic.
2. the author's conclusion that Jesus ultimately lived somewhere else (but not on earth) until he reached middle age and then died. This view is not shared by the majority of Islamic scholars. Rather, most scholars believe that Jesus was raised to God and will eventually return to lead the Muslims. Therefore, the theory that he lived in some unknown world is not in line with orthodox Islamic belief.
Other than that, this is a good book and I would recommend it to anyone.